1. Field
The present invention relates generally to imaging probes based on triggered molecular geometry.
2. Background
Microscopic imaging is a powerful tool for studying biologic systems. At the heart of microscopy is the imaging probe, which transduces invisible biological information, such as an mRNA sequence to an imageable signal. At present, imaging probes are mostly constructed by engineering the optical, chemical, and physical properties of imaging probes to produce tailored optical properties. Commonly used imaging probes such as fluorescent proteins (e.g. green fluorescent protein (GFP) and red fluorescent protein (RFP)) and small-molecule dyes (e.g. DAPI, fluorescein, and rhodamine) rely on fluorescence to transduce biological information into an imageable signal. A key challenge in fluorescence bioimaging is the detection many distinct targets simultaneously. Using current practices, between 3 and 6 fluorescent species can be spectrally resolved, setting an upper bound to the number of probes that can be simultaneously employed. This limitation presents a significant technical hurdle in the study of gene expression using single cell fluorescence microscopy, where the number of spectrally distinguishable fluorophores sets an upper bound for the distinct mRNA species that can be simultaneously monitored in a cell.
Another imaging technique, cryo-electron tomography, also known as electron cryotomography, is a type of electron cryomicroscopy that can be used to obtain structural details of complex cellular organizations at subnanometer resolutions. Electron cryotomography uses tomography to obtain a 3D reconstruction of a sample from tilted 2D images at cryogenic temperatures. This enables the study of organelles and the supramolecular architecture of cells in a native state. A long standing challenge in electron cryotomography, however, is the lack of visual markers that can be used to uniquely identify the target proteins.